Positive displacement pneumatic motors are used in a variety of applications because of their inherent ease of use, constant force output, safe operation in explosive environments, among other reasons. They function by supplying compressed gas to either a piston or diaphragm that then pushes against a load such as a pump. At the end of each stroke, the motor must exhaust the high pressure air and move in the opposite direction to repeat the cycle. This uncontrolled expansion of air at the end of the motor stroke can generate considerable and sometimes dangerous amounts of noise. The exhaust gas is also cooled by the expansion process. Any moisture present in the gas can condense and freeze, creating ice. If the ice is allowed to build up, it can inhibit or cease operation of the motor.